The present invention relates to improvements to polyetherimide resins. More particularly, the present invention relates to polyetherimides which are melt crystalline.
The polyetherimides form a now well-known class of engineering thermoplastic polymers. These polymers offer such attributes as high heat resistance, stiffness, impact strength and transparency, high mechanical strength, good electrical properties, high flame resistance, low smoke generation and broad chemical resistance. In addition to these important properties, the polyetherimides exhibit the ease of processability associated with traditional engineering thermoplastics, although in general higher melt temperatures are required.
Polyetherimides are sold by the General Electric Company under the trademark Ultem.RTM.. Polyetherimide resins are of considerable commercial value for use in molding compositions because of the excellent physical, chemical and thermal properties mentioned above. The high glass transition and heat deflection temperatures exhibited by these polymers permit their use in high performance applications. The polyetherimides find applications in the automotive, aerospace and electrical industries, for example.
It is well known and accepted by those skilled in the art that the conventional, commercially available polyetherimides exist in an amorphous state upon solidifying from the melt This is true of the polyetherimide resins commercially available from the General Electric Company under the ULTEM.RTM. trademark including ULTEM-1000 (a copolymer of bisphenol A dianhydride and meta-phenylene diamine), ULTEM-6000 (a copolymer of bis phenol A dianhydride, pyromellitic dianhydride and meta-phenylene diamine) and ULTEM-5001 (a copolymer of bisphenol A dianhydride and para-phenylene diamine).
Various efforts have been made to improve even further the properties of polyetherimide resins. One approach to such improvements has been to prepare melt crystalline forms of the resins An increased solvent resistance is one example of an improvement that might be achieved by increasing the melt crystallinity of the resins.
Examples of melt crystalline polyetherimides using exotic diamines are described by Takekoshi, et al., in Journal of Polymer Science, 74, pp. 93-108 (1986). The use of an exotic diamine, 1,3-bis(4-aminophenoxy)-benzene allowed certain polyetherimides to be melt crystalline and yielded higher solvent resistance to ordinary chemical reagents which are used for industrial purposes The disadvantages of these types of `exotic diamine` polyetherimides are scarcity and high price of the amines.
It is one object of the present invention to provide melt crystalline polyetherimide resin compositions Another object of the invention is to provide such compositions which retain the ease of synthesis and processing associated with the commercially available amorphous polyetherimide resins. A further object of the invention is to provide melt crystallizable polyetherimide resin compositions having production costs permitting them to become commercially attractive to industry.